Motor neuron diseases (MNDs) are diseases which lead to impairment of the motor nerve functions due to the loss of motor neuron cells and degenerative changes in the motor pathways of the central nervous system, and are essentially different from neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, and cerebellar atrophy and the like, because they involve damages to other nerve cells. These MNDs include, in addition to amyotrophic lateral sclerosis (also known as Lou Gehrig's disease), diseases which are classified into primary lateral sclerosis (PLS) affecting only upper motor neurons, progressive muscular atrophy (PMA) affecting only lower motor neurons, progressive bulbar palsy (PBP) affecting lower motor neurons of the brain stem, and the like.
Amyotrophic lateral sclerosis (ALS; also known as Lou Gehrig's disease) is one of the motor neuron diseases (MNDs), and is a neurological disease which selectively affects motor neurons only, although the pathological mechanism is still not known clearly (Haverkamp L J et al., Validation of a scoring system and a model for survival prediction Brain 1995; 118:707-19., Caroscio J T et al., Neurol Clin 1987; 5:1-9). ALS causes, from a pathological aspect, the loss of pyramidal cells in the cerebral motor cortex (i.e., giant Betz cells), anterior spinal motor neurons and brain stem motor neurons, and degeneration thereof into pyramidal cells; while ALS shows, from a clinical aspect, both upper motor neurons and lower motor neurons signs, and shows rapid clinical deterioration after onset of the disease, thus leading to death within a few years. An incidence rate of ALS corresponding to 1 to 2 persons and a prevalence rate corresponding to 4 to 6 persons, out of a population of 100,000 are reported, while the incidence rate is 1.5-fold higher in men than in women, but the incidence rates become similar to each other at an age of from 50's to 60's.
The only safe drug used for treating ALS is riluzole, which has an antagonistic effect against glutamate, and has been approved by the US Food and Drug Administration (FDA) for commercialization. However, this drug shows unsatisfactory efficacy, which means currently there is no definite therapy for ALS that can improve rapidly deteriorating clinical conditions.
Recently, various attempts to treat the nerve system disorders, including ALS, have been conducted using stem cells. For example, Korean Patent Application Publication No. 2005-0012208 discloses that mesenchymal stem cells are cultured in a medium containing an epidermal growth factor and a hepatocyte growth factor, and then differentiated and expanded into nerve cells, which are in turn transplanted into a patient to treat a nerve system disease. However, the method as disclosed in this patent application is a method for transplanting the nerve cells, which had been differentiated from mesenchymal stem cells, and the method requires a complex process and a long period of time to induce their differentiation
In this regard, the present inventors have conducted research on a new method for treating motor neuron diseases, particularly ALS, and found that when mesenchymal stem cells (MSCs) of their own are isolated and expanded ex vivo to obtain a sufficient number of cells, and the cells are employed for cell therapy in animal models as well as patients with ALS diseases, rapid clinical deterioration is mitigated in the patients, and a significant therapeutic effect is obtained, thereby completing the present invention.